A critical and a pressing need exists presently for a delivery system that, (1) delivers a beneficial drug at a controlled rate and continuously in a biological environment having a pH of greater than 3.5 to 8.0 such as the intestine of an animal but, (2) does not deliver the drug in a biological environment having a pH of 1.0 to 3.5 inclusive, such as the stomach of an animal. The need arises because often it is contra-indicated and therapeutically undesirable to deliver many drugs in the stomach, and because often it is indicated and therapeutically desirable to deliver many drugs in the intestine. That is, some drugs do not lend themselves for delivery in the stomach, while some drugs lend themselves for delivery primarily in the intestine.
For example, drugs where administration in the stomach should preferably be avoided include, (a) drugs that are digested or decomposed in the acidic environment of the stomach such as the antibiotics erythromycin and carbenicillium; (b) drugs that induce nausea and vomiting such as emetine, atabrine and diethylstilbestrol; and, (c) drugs that act as stomach irritants such as chloride and iron salts, and anti-inflammatory drugs like aspirin, flufenamic acid, and phenylbutazone.
For example, drugs where administration in the intestine is preferred include, (d) intestinal antihelmitics such as bephenium hydroxynaphthoate, niclosamide, piperazine, thiabendazole and dichlorophen; (e) intestinal antibacterials such as methenamine, sulphasalazine and phthalylsulphthiazole; (f) antischistomals such as niridazoli; (g) antiprotozians such as dichlorophen; and, (h) drugs where it is desirable to dispense the medication in the intestine for initial absorption in the duodenum and jejunium, such as folic acid in the normal proximal jejunum.
The above presentation clearly teaches both the necessity and the urgency for a unique delivery system that substantially avoids delivering a drug in the stomach, but which delivery system can administer a drug in a therapeutically effective amount in the intestine over time. It will be appreciated by those versed in the drug dispensing art in view of this presentation, that if a delivery system is provided that can fulfill these demands, such a delivery system would have a positive value and represent also a substantial contribution to the dispensing art. Likewise, it will be appreciated by those skilled in the art, that if a delivery system is made available for releasing drug at a controlled rate over time in the intestine for achieving therapeutic levels, such a delivery system would be clinically useful in the practice of medicine.